Fix typo enabling pprof (#114)

Nothing critical, but had a typo in the naming of the config entry to enable `pprof`.

Co-authored-by: josef <josef.nilsen@outlook.com>
Reviewed-on: https://gitea.com/gitea/helm-chart/pulls/114
Reviewed-by: luhahn <luhahn@noreply.gitea.io>
Reviewed-by: Lunny Xiao <xiaolunwen@gmail.com>
Co-authored-by: JosefWN <josefwn@noreply.gitea.io>
Co-committed-by: JosefWN <josefwn@noreply.gitea.io>

README.md

@@ -304,7 +304,7 @@ gitea:
 
   config:
     server:
-      PPROF_ENABLED: true
+      ENABLE_PPROF: true
 ```
 
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